JPH06178115A - Image processor - Google Patents

Abstract

PURPOSE:To simplify the work of an operator and to reduce his burden by automatically obtaining an optinum gradation conversion curve and performing gammacorrection in accordance with this conversion curve only by designating an area on a displayed image. CONSTITUTION:An original image in a state that a gamma correction circuit 5 is not interposed is displayed by an image display device 3 and arbitrary areas A, B are designated by the operation of a mouse 4. The densities of the average value and the peak value within each area of these points A, B are read by a CPU 2 and inputted in an approximate expression calculation circuit 6. Then, the circuit 6 determines a polynomial showing the input/output characterisitic curve from these two point data by an approximate calculation. A data calculation circuit 1 calculates each value of the output image data corresponding to each value of input image data from this polynomial. A writing circuit 8 designates the address corresponding to each value of input image data and writes each output image data in the gamma correction circuit 5. Therefore, a gradation conversion is performed for image data via the circuit 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, and more particularly to image processing suitable for .gamma. Correction (gradation correction) of medical digital images such as X-ray fluoroscopic images, X-ray CT images and MR images. Regarding the device.

[0002]

2. Description of the Related Art Medical digital images such as X-ray fluoroscopic images, X-ray CT images, and MR images are hard to see by the human eye if the pixel values are directly displayed in correspondence with the density (luminance). , It is necessary to display after performing appropriate gradation conversion. Conventionally, this gradation conversion characteristic is selected from the specific conversion curves which the operator judges by visual inspection to be the easiest to see, or the operator reads the image characteristics such as the density distribution. The optimum conversion curve is set manually.

[0003]

However, in the prior art, since the gradation conversion characteristic is ultimately determined by relying on the operator's sense, the operator's burden is heavy and optimum setting is required unless the operator is a proficient operator. There is a problem that you can not.

In view of the above, the present invention has been improved in such a way that the gradation conversion characteristics can be set semi-automatically to simplify complicated work and reduce the burden on the operator. The purpose is to provide.

[0005]

In order to achieve the above object, in an image processing apparatus according to the present invention, gradation correction means for converting the gradation of image data input to the image display means,
A means for controlling this, a means for designating an arbitrary area on the displayed original image, and a means for obtaining an optimum gradation conversion curve from the pixel value of the designated area are provided. The feature is that the gradation correction means is controlled according to the curve.

[0006]

When an arbitrary area is designated on the displayed original image, the pixel value of the designated area is read, and the optimum gradation conversion curve is automatically obtained from it. Then, the gradation correction means is controlled according to the optimum gradation conversion curve, and the gradation conversion is performed according to the conversion curve. Therefore, if the operator manually specifies only the area, the optimum gradation conversion curve is automatically obtained after that, and gradation conversion is performed according to the conversion curve. It is easy, and the burden on the operator can be reduced because it does not depend on the skill and sense of the operator.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows an image processing apparatus according to an embodiment of the present invention. In FIG. 1, the image memory 1 stores, for example, digital image data of an X-ray fluoroscopic image, which is stored in the CPU 2
After that, the image is sent to the image display device 3 and displayed. For example, a display as shown in FIG. 2 is displayed on the display screen of the image display device 3.

A coordinate input device such as a mouse 4 and a trackball (not shown) is connected to the CPU 2, and an arbitrary area can be designated by operating the coordinate input device. The operator manually operates the mouse 4 to specify, for example, two small areas A and B on the display image of FIG.

A gamma correction circuit 5 is connected to the CPU 2 so that the gradation of image data to be sent from the image display device 3 can be corrected. The γ correction circuit 5 is composed of, for example, a RAM, and when the address is designated by each pixel value of the input image data, the pixel value of the output image data stored at the address is read out, so that the input / output conversion is performed. And the gradation conversion is performed.

The output data to be stored at each address of the γ correction circuit 5 is written by the writing circuit 8. Therefore, by arbitrarily changing the output data written by the writing circuit 8, it is possible to correspond to any gradation conversion curve. The output data to be written is calculated by the data calculation circuit 7 according to the approximate expression obtained by the approximate expression calculation circuit 6.

First, the image display device 3 displays the original image without the γ correction circuit 5, and the arbitrary regions A and B are designated by operating the mouse 4 as described above. The areas A and B are areas of the image that are most interesting and are desired to have contrast. Then, the CPU 2 reads the density (pixel value) of the average value and the peak value in each of the two areas A and B,
This is input to the approximate expression calculation circuit 6.

Then, the approximate expression calculation circuit 6 obtains a polynomial representing the input / output characteristic curve of FIG. 3 from the data of these two points by approximate calculation. At that time, a curve is required so that the contrast width x% of the region of interest and the offset amount y% corresponding to the center point of the input data are optimal when the overall contrast width of the output image data is 100%. .

Since the polynomial (each coefficient of the polynomial) representing the curve of FIG. 3 is obtained in this way, the data calculation circuit 7 calculates each value of the output image data corresponding to each value of the input image data from this polynomial. Then, the writing circuit 8 writes each output image data by designating the address corresponding to each value of the input image data in the γ correction circuit 5.

Then, the image data read out from the image memory 1 and sent to the image display device 3 is subjected to gradation conversion (input / output conversion) according to a curve as shown in FIG. It will be. Thus γ
The corrected image is displayed on the image display device 3.

Although two areas A and B are designated on the image displayed on the image display device 3 in the above description, one larger area covering the entire area of interest, for example, the rectangular area C in FIG. 2 is designated. You may do it. In this case, the maximum value and the minimum value of the pixel values in the area C are read, and the optimum gradation conversion curve is obtained from this in the same manner as above.

Various means are conceivable for the means for reading the average value and the peak value of the pixel values in the designated area, and any means may be used. Further, the size and the number of designated areas are not limited to the above, and may be various.

Furthermore, in the above, the optimum gradation conversion curve is obtained by polynomial approximation, but the present invention is not limited to this, and any method that can obtain the optimum gradation conversion curve may be used. Further, in the above description, the contrast width and the offset amount are automatically obtained, but it is also possible to manually set them arbitrarily.

Although the above-mentioned embodiment has a hardware-like configuration, the CPU 2 performs software to obtain the optimum gradation conversion curve, calculate each data from it, and write each data. Of course, it can be configured.

[0019]

As described above, according to the image processing apparatus of the present invention, the optimum gradation conversion curve is automatically obtained only by designating the area on the displayed image. Since the γ correction is performed according to the curve, the work of the operator can be simplified and the burden on the operator can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a display image in the embodiment.

FIG. 3 is a diagram showing an example of a gradation conversion curve.

[Explanation of symbols]

 1 Image Memory 2 CPU 3 Image Display Device 4 Mouse 5 γ Correction Circuit 6 Approximation Formula Calculation Circuit 7 Data Calculation Circuit 8 Writing Circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G06F 15/68 310 9191-5L

Claims (1)

[Claims] 1. An image display unit for displaying an image in accordance with input image data, a gradation correction unit for converting the gradation of image data input to the display unit, and an original displayed by the display unit. Means to specify any area on the image,
An image processing apparatus comprising: means for obtaining an optimum gradation conversion curve from pixel values in a designated area; and means for controlling the gradation correction means according to the optimum gradation conversion curve.